CESTODES : BIOLOGY 211 



todes often appears to be brought about by alterations in the scolex, 

 such as loss of the hooks, atrophy of the suckers and ros- 

 tellum, finally the dropping off of the scolex ; it is unknown 

 whether the chain of segments deprived of its scolex likewise 

 then perishes or first attains maturity. It has already been men- 

 tioned that in a few species the foremost proglottides are trans- 

 formed into organs of attachment on the normal loss of the scolex. 

 Abnormalities and malformations are encountered relatively frequently 

 in the Cestodes such as abnormally short or long segments ; the so-called 

 triangular tapeworms, which if belonging to the tsenia always possess six 

 suckers ; often also club-shaped segments occur between normal ones, or 

 there may be a defect (fenestrated segments) in one segment or in the centre 

 of a number following one another ; bifurcated chains of segments have likewise 

 been observed, as we'll as incomplete or complete union of the proglottides, 

 abnormal increase of the genital pores, reversion of the genitalia. Besides 

 the above-mentioned increase of the number of suckers on the scolex 

 (in taenia), there maybe a decrease in the number; in other cases the crown 

 of hooks may be absent, or abnormally-shaped hooks may be formed. 



LITERATURE. 



The literature of the Cestodes up to 1895 is comprised in my work on 

 Cestodes, in Bronn's Cl. u. Ordn. d. Thierr (iv., 2). Of the more recent works 

 the following deserve mention : 



BLANCHARD, R. Sur quelq. Cest. monst. (Progr. med., 1894 [2], xx.) 

 BRANDES, G. Teratolog. Cestod. (Ztsch. f. Nat., 1899, Ixxii., p. 105.) 

 BLOCHMANN, F. Die Epithelfr. b. Cest. u. Trem. Hbrg., 1896. 

 CATTAERT, P. A. Contr. a 1'et. d. Ten. triedr. (Arch, parasit., 1899, ii., p. 153.) 

 COHN, L. Z. An. d. Vogelcest. (Z. f. w. Zool., 1900, Ixvii., p. 255.) 



Unters. lib. d. centr. Nervens. der Cest. (Zool. Jahrb. An., 1898, part xii., 



p. 89.) 

 Z. Anat. u. Syst. d. Vogelcest. (Nov. Act. Ac. Caes. Leop. -Carol. Nat. Cur., 



Ixxix., No. 3, Halle, 1901.) 

 FUHRMANN, O. Arbeiten iiber Vogeltaenien in : Rev. suiss. de Zool. et Ann. Mus. 



d'hist. nat. Geneve, iii., iv., v., vii. ; C. f. B., P. u. I. [i], xxvi. 

 Ueb. Prosthecocotyle. (Ibid., xxv.) 

 Neuere Vogelcest. (Ibid., xxix.) 



JACOBI, A. Diploposthe laevis. (Zool. Jahrb., 1897, x.) 

 LUKE, M. Beitr. z. Kenntn. d. Bothriocephaliden. (C. f. B., P. u. L, 1899 



[i], xxvi., p. 720 ; 1900, xxvii., p. 200.) 



Z. Anat. u. Syst. d. Bothr. (Verb. d. D. zool. Ges., 1899, p. 30.) 

 Unters. iib. Bothr. mit. marg. Genit. (Z. f. w. Zool., 1900, Ixviii.) 

 Revis. m. Bothr.-Syst. (C. f. B., P. u. I. [i], Orig., 1902, xxxi., p. 318.) 

 PINTNER, TH. Rhynchodaaldriis. b. Tetrarh. (Arb. zool. Inst. Wien., 1899, xii.) 

 RIGGENBACH, E. Genus Ichthyotaenia. (Rev. Zool. Suisse, 1896, iv.) 

 STILES, CH. W., and A. HASSAL. Tapeworms of Poultry. U. S. Dep. of Agric. 



Bur. of an Ind. Bull., 12, Wash., 1896.) 

 STILES, CH. W. Rev. of ad. Tapew. of Hares and Rabb. (Proc. U. S. Nat. 



Mus., 1896, xix.) 



VAULLEGERAD, A. Rech. s. 1. Tetrarhynq., These, Paris, 1899. 

 WOLFFHUGEL, K. Beitr. z. Kenntn. d. Vogelhelm. In.-Diss., Basel, 1900. 

 ZERNECKE, E. Unters. iib. d. fein. Bau d. Cest. In.-Diss., Rostock, 1895. 

 ZSCHOKKE, F. Cest. d. Mars. u. Monotr. (Semon: Zool. Forsch. in Austr. u. 



d. Mai. Arch. [Jen. Denkschr., 1898, viii.], v.) 

 Neue Stud, an Cest. aplac. Saugeth. (Z. f. w. Zool., 1899, lxv. f p. 404. > 



